<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="./vue.js"></script>
</head>

<body>
    <div id="app">
        <p>当前页面为{{page}}</p>
        <button v-for="(item) in 5" @click="page=item">{{item}}</button>
    </div>
    <script>
        Vue.config.productionTip = false;
        const vm = new Vue({
            el: "#app",
            data() {
                return {
                    page: 1
                };
            },
            watch: {
                // page(newUle, oldUle) {
                //     //  当侦听的数据改变时,就会执行该函数
                //     console.log(newUle, oldUle);
                // }
                //  完整写法

            }
        });
    </script>
</body>

</html>